Turbocloud development

ABSTRACT

A powder cloud development device for developing a latent electrostatic image with toner wherein the toner is conveyed to the latent image area by a forced air system. A development electrode is mounted adjacent the image area to improve development and the electrode includes means to induce turbulence in the flow. A precipitation roller collects the toner in the flow after it passes the image area to control the toner concentration circulating in the device.

United States Patent [72] Inventor Ernest A. Weiler Rochester, N.Y. [21]App1.No. 838,951 [22] Filed July 3, 1969 [45] Patented Jan. 11, 1972[73] Assignee Xerox Corporation Rochester, N.Y.

[54] TURBOCLOUD DEVELOPMENT 17 Claims, 7 Drawing Figs. [52] U.S. Cl118/629, 117/17.5,118/312,118/637 [51] Int. Cl G03g 13/08 [50] Field ofSearch 1 18/629, 627, 637, 308, 312, 309; 117/17.5

[56] References Cited UNITED STATES PATENTS 2,876,737 3/1959 Carlson118/312X 3,002,849 10/1961 Harmon et a1. 118/308 X POTENTIAL 3,008,82611/1961 Mott et al. 117/17.5 X 3,336,905 8/1967 Lehmann 118/6373,357,399 12/1967 Fisher 118/637 3,357,403 12/1967 Donalies 117/17.53,367,306 2/1968 Lawes et a1. 1l7/17.5 X 3,370,529 2/1968Micha1chik..... l17/17.5 3,484,265 12/1969 Swyler 118/637 X PrimaryExaminer-Mervin Stein Attorneys Donald F. Daley, James J. Ralabate andRobert W. Mulcahy ABSTRACT: A powder cloud development device fordeveloping a latent electrostatic image with toner wherein the toner isconveyed to the latent image area by a forced air system. A developmentelectrode is mounted adjacent the image area to improve development andthe electrode includes means to induce turbulence in the flow. Aprecipitation roller collects the toner in the flow after it passes theimage area to control the toner concentration circulating in the device.

BIAS POTENTIAL PMENIEU JAM 1 I872 SHEET 1 [IF 2 BIAS POTENTIAL FIG. 2

BIAS POTENTIAL INVENTOR.

ERNEST A WEILER MQQQM PATENTEU JAN: 1 I972 SHEET 2 OF 2 TURBOCLOUDDEVELOPMENT BACKGROUND OF THE INVENTION This invention relates ingeneral to developing a latent el'ectrostatic image and in particular toan improved powder cloud development device.

More specifically, this invention relates to a powder cloud developmentdevice wherein a forced air system carries toner to a latentelectrostatic image area by means of a turbulent high-velocitymultidirectional airflow to prevent directional development effects. Aprecipitation roller receives and collects toner after it passes thephotoconductor to control the concentration oftoner in cloud.

In the process of xerography, a xerographic plate comprising a layer ofphotoconductive material on a conductive backing is given a uniformelectric charge on its surface and then is exposed to subject matter tobe reproduced by various projection techniques. This exposure dischargesthe plate in accordance with the light intensity reaching it, therebycreating a latent electrostatic image on or in the plate. Development ofthe image is effected by developers which may comprise, in general, amixture of suitable, pigmented or dyed resin base powder, hereinafterreferred to as toner, which is brought into contact with the plate byvarious well-known development techniques. During such development ofthe image, the toner powder is brought into surface contact with thephotoconductive coating and is held there electrostatically in a patterncorresponding to the latent electrostatic image. Thereafter, thedeveloped xerographic image may be transferred to a support material towhich it may be fixed by any suitable means such as heat fusing.

An example of one of the aforementioned techniques for developing thelatent image is disclosed in Walkup, U.S. Pat. No. 2,618,551, whereinthe toner carried by carrier particles, is rolled or cascaded over thelatent electrostatic image bearing surface. The carrier particles insuch a system are much larger than the individual toner particles andare selected to be of a material that will form a triboelectric bondbetween the carrier and the toner. In such a relationship the carrierand toner will acquire an opposite electrostatic charge resulting in thetoner being charged to polarity opposite that of the latent chargedimage. In practice, each carrier has numerous toner particles attractedthereon allowing them to be transported into contact with thephotoconductor whereat the greater electrostatic attraction between thetwo developer components causing toner to be stripped off the carrierand electrostatically bonded to the charged image to effect developmentthereof. Such a technique is known in the art as cascade development.

Several difficulties are associated with the cascade developmentprocess. For example, in developing large image areas the electric fieldof the image is stronger at the edges than in the center portion.Therefore, the lines of force at the edges are sufficient to attracttoner from the carrier, but in the center portion of the image toner isnot attracted since the field is not strong enough to overcome thetriboelectric attraction between the two components of the developer.Such a phenomenon results in an incomplete development in the centralportions of the image while the edges are sufficiently developed.

Cascade development also requires a thorough intermixing of developerafter repeated development of an image. If intermixing does not occur, adefect in development referred to as image striations results because ofcarrier material becoming depleted of toner powder. Normally, tonerdepletion occurs in cascade development when the carrier and tonermaterials move past the image in one direction across thephotoconductor. Since images normally having varying sized latent imageareas to be developed along the direction of flow, repeated developmentcauses the developer flow moving past the more massive image areas to bedepleted of toner in a greater amount than the less massive image areas.Elaborate systems for intermixing the developer material is required toovercome this toner depletion difficulty.

In order to overcome the difiiculties presented by the cascade method atechnique of developing an image, referred to as powder clouddevelopment, has been given much attention in the prior art. An exampleof the powder cloud technique is disclosed in Carlson, U.S. Pat. No.2,928,575, wherein a powder cloud is created by air pressure and acharge placed on the toner by the contact of the cloud on the wall ofthe powder cloud generator. The charged toner cloud thereupon is movedinto the vicinity of the charged image for the development thereof.Accordingly, the powder cloud method alleviates some of the difficultiesof large area development because the electrostatic field of the imagedoes not have to compete with the triboelectric attraction between thetoner and the carrier as in the cascade system. Therefore, the powdercloud developing system allows the toner to more readily affix to theweaker electrostatic attraction of the central portion of the image.

However, other problems are associated with the use of prior art powdercloud development devices. One disadvantage associated with thesedeveloping systems is the ease at which the charged toner will affix tothe nonimage or residual charge areas of the photoreceptor. This resultsin development of what is known as background areas and, therefore,while the prior art powder cloud devices achieve more completedevelopment of solid image areas this method at the same time producesthe disadvantage of developing unwanted background areas. In an attemptto prevent development of nonimage or background areas, the prior arthas employed the use of a development electrode in the powder clouddevice to increase the electric field in image areas in order to attemptto insure that the increased strength of the image field would morereadily receive toner to the exclusion of the background areas. However,the use of development electrodes has not completely alleviated thedevelopment of nonimage areas and it remains desirable to overcome thebackground toner deposition problem of the existing powder cloudtechniques.

Another attempt in the prior art to solve the aforementioned backgrounddevelopment problem has been to create a powder cloud flowing past theimage at a sufficient velocity to prevent the toner from being attractedby the weak electric field of the background area while allowing thegreater field of the image areas to deflect and attract the toner. Itwas believed that such a velocity toner flow would prevent backgrounddevelopment and at the same time insure adequate toner adherence to thecharged laten image. The achievement of high-velocity toner flow,however, has been difficult to obtain as well as making prior artdevices more expensive and complex. Further, the generation ofhigh-velocity toner cloud flow conditions in prior art devices hascaused directional effects which appear as a streaking of the developedimage since the toner passes the photoconductive surface in only onedirection. In order to obtain better quality xerographic development, itis necessary to provide a powder cloud device which does not producestreaking of the image as in the prior art.

Satisfactory development by use of a powder cloud device has in the pastproven to be expensive and complex. A further reason for this difficultyis the necessity to maintain a controlled dispensing of the toner intothe airflow to insure a uniform concentration. If the toner in the cloudis not uniformly dispersed, agglomerates of toner particles are formedwhich result in uneven development of the charged image. Also, in orderto provide economy of operation by powder cloud development, anefficient retrieval of the unused toner must be provided to prevent lossto the outside of the device. Therefore, it becomes desirable to providea relatively simple powder cloud developing device which rendersefficient development of a charged image and overcomes background anddirectional problems of conventional devices.

3 SUMMARY OF THE INVENTION It is, therefore, an object of this inventionto improve development of latent electrostatic charge patterns in imageconfiguration.

Another object of this invention is to improve latent electrostaticimage development by preventing the development of background areas of acharged image.

A further object of this invention is to improve latent electrostaticimage development by passing a toner powder cloud in multiple directionsto prevent directional development effects on the developed image.

Still another object of this invention is to improve powder clouddevelopment by recirculating the powder cloud past the latentelectrostatic image to more efficiently utilize the electroscopic tonerpowder and minimize the air filtration system.

A still further object of this invention is to improve latentelectrostatic image development by maintaining the concentration of thetoner in a powder cloud development device at a regulated level.

These and other objects are obtained in accordance with the presentinvention wherein there is provided a powder cloud device which utilizeshigh-velocity flow created by an air fan to effect development of alatent electrostatic image. Further included in the novel devicesdisclosed herein is a development electrode adjacent the charged imageto create a uniform electrical field emanating therefrom to achievebetter solid area development. The electrode is formed to induceturbulence in the toner cloud flow to insure that the toner passes theimage in a plurality of directions to prevent directional ef fects orstreaking of the developed image. The present invention also includes aprecipitation roller which removes toner from the toner cloud after itpasses the image to prevent unused toner from being reintroduced to theimage thereby producing undesirable background development and to insurethat the concentration of the toner in the flow remains at a desiredlevel. The precipitation roller is electrically biased or is constructedof a material that will cause unused toner to adhere to its surface tothereafter be returned to a toner reservoir for redispensing into theairflow.

By utilizing the high-velocity flow of toner powder as in the presentinvention, the background areas do not attract the toner while theelectrostatic charge in the image areas is sufficient to attract andretain the particles thereon. Further, by agitating the flow so that thetoner cloud moves past the charged image in multiple directions, theaforementioned streaking problem is prevented. Also, the precipationroller improves development of the charged image since control of tonerconcentration is achieved to insure that the optimum amount of toner isflowing in the cloud. Therefore, the present invention achieves thedesired results of reducing background development, maintaining theconcentration of toner at desired levels, preventing development defectcharacteristics, and other readily apparent advantages with a devicethat is less expensive and more efficient than prior art powder clouddevices.

DESCRIPTION OF THE DRAWINGS Further objects of the invention togetherwith additional features contributing thereto and advantages accruingtherefrom will be apparent from the following description of severalembodiments of the invention when read in conjunction with theaccompanying drawings wherein:

FIG. 1 is a schematic illustration ofa xerographic reproducing machineutilizing the powder cloud development devices according to the presentinvention;

FIG. 2 is a perspective illustration of one embodiment of the powdercloud development device according to the present invention;

FIGS. 3, 4 and 5 are perspective illustrations of embodiments of thedevelopment electrode utilized in the powder cloud development devicesaccording to the present invention;

FIG. 6 illustrates a schematic diagram of the flow of air in theembodiment shown in FIG. 5 and;

FIG. 7 illustrates a perspective illustration of a second embodiment ofapowder cloud development device according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, there isshown a schematic view of a drum-type xerographic reproducing machineutilizing the present invention. The central element of the apparatus isa photoreceptive drum I mounted on suitable rollers and rotata ble in aconventional direction by a motor M. The drum I is covered on the outersurface 2 with a layer of photoconduc tive insulating material such asvitreous selenium or other suitable surface. A uniform electrostaticcharge is placed on the photoconductor surface of the drum by means of acon ventional corona charging device 3. The uniformly charged surface ofthe drum is then rotated to an exposure means 4, of any well-known type,that exposes the charged image to copy to be reproduced to thereby forma latent electrostatic image of the copy on the photoconductor drumsurface.

Following the formation of a latent electrostatic image of the copy, theimage on the drum will rotate to a development station 5 (to bedescribed in detail later) to bring the charged image into contact withdeveloper to affix toner powder thereto. After development, the tonerimage moves to a transfer device 6 and the powder is transferred fromthe drum to a support material shown as a web of paper 7 or the likewhich is positioned in contact with the drum by rollers 8 and 9. Asecond corona charging device 10 applies a charge to the back of the webto facilitate transfer of the toner in image form. The toner image onthe support web then moves past a heating element 11 which affixes thetoner to the paper web to form a duplicate of the original copy. Acleaning device 12 contacts the image area of the drum surface as itleaves the transfer device 6 to remove any residual image material fromthe drum to facilitate reuse of the surface. It should be clear thatother modes of charging, exposing, transfer and fusing may be utilizedin connection with the present invention, or in a system wherein thephotoreceptor is carried by the support material.

Referring now to FIG. 2, there is illustrated one embodiment of thepowder cloud development device 20 at develop ment station 5 accordingto the present invention. This embodiment of the invention creates ahigh-velocity cloud of toner powder in a flow of air by utilizing fan 21which forces air in the direction of the arrows on the drawing through acloud chute 22. A reservoir 23 oftoner is supported above the chute toretain a supply of toner and the supply is dispensed into the cloudchute by a toner dispensing roller 24 to control the concentration ofthe toner introduced into the airflow created by the fan 21. Suchregulation of the dispensed toner is effected by the rotation of thedispensing roller 24 by suitable means (not shown) to turn at a ratedepending on the desired amount of toner concentration. As the rollerincreases its rotative speed, a larger amount of toner is introducedinto the cloud chute by the roller, since the roller carries a fixedamount of toner on its surface and as it rotates faster a greaterquantity will be dropped into the chute for any given time interval.

To provide dispensing ofcharged toner into the cloud chute 22 thedispensing roller 24, being constructed of a material which forms atriboelectric relationship between it and the particles, further acts toplace an electrostatic charge on the toner. As an alternative manner ofcharging the toner, the roller may be electrically biased by beingconnected to a suitable source of electrical potential to place a chargeon any toner in contact with the roller 24. A nozzle 25 is provided inthe cloud chute immediately upstream of the dispensing roller toincrease the velocity of air generated by the fan insuring that thetoner is uniformly distributed and carried in the form of a cloud. Thecloud chute can be electrically biased to prevent toner from clinging tothe chute and to charge any toner particles which were not effectivelycharged by the dispensing roller. The flow of air carrying the cloud ofcharged toner particles moves at a high velocity through the cloud chute22 and is directed through a space between the development electrode 30and the photoconductive drum 1 bearing the latent charged image on itssurface.

The development electrode 30 is a grounded conductive member having asurface in direct confrontation to the charged image and, therefore,alters the lines of electrostatic force emanating from the latentelectrostatic image. As the high-velocity charged toner passes betweenthe charged image and the development electrode 30, the relative highspeed of the particles prevents toner from depositing on the low-chargebackground areas while the electrical field of the electrostatic imagewill attract the toner for development. Therefore, it should be cleartat the cooperation of high-velocity flow and the development of acharged image by preventing deposition of toner in nonimage areas. Thedevelopment electrode 30 may further increase the field of the chargedimage and neutralize the background field by being connected to asuitable bias potential which provides still greater control of thedevelopment of the image.

To prevent toner loss to the outside of the device, a suitable seal 26is provided between the development unit and the photoconductor. Theseal 26 is desirably constructed of a lowfriction material such as, forexample, rabbit fur to prevent abrasion to the photoconductive surface2. As a further prevention of toner loss, a precipitation roller 31 isrotatably mounted and driven by a suitable means (not shown) beneath anelectrically biased baffle 32 to collect unused toner after it passesbetween the photoconductive surface and the development electrode. Theprecipitation roller 31 is formed of a material having a triboelectricattraction to the charged toner causing the toner to cling thereto andprecipitate out of the airflow. As an alternative manner of attractingthe toner, the roller 31 may be connected to a suitable potential of apolarity opposite to the charge on the particles.

The biased baffle 32 is connected to an electrical potential of the samepolarity as the charge on the toner to perform the dual function ofrepelling the toner therefrom to the precipitation roller. The flow ofair which has been denuded of toner by the precipitation roller 31 thenflows beneath the baffle and up into a duct 33 to be returned in cleanedform to the fan 21 for recirculation. To assure that no toner remains inthe return airflow, a suitable filter 34 is provided at the entrance ofthe duct to remove any toner not already collected by the precipitationroller 31.

The roller is rotatably mounted to rotate by suitable means (not shown)and thus allow the toner collected on the precipitation roller to bescraped from the surface by a suitable scraper 35, such as, for example,a means flexibly biased there against. The removed toner falls into thetoner reservoir to be metered into the airflow by the toner dispenser24. It should, therefore, be apparent that the novel powder cloud deviceof the embodiment described herein in conjunction with FIG. 2 providesimproved development of a latent electrostatic image by preventingdeposition of toner in nonimage areas through the utilization of adevelopment electrode and high-velocity toner flow and controls theconcentration of the toner in the system by removing unused toner fromthe airflow prior to recirculation.

Referring now in particular to FIG. 3, there is illustrated another formof the development electrode 40 shown in the embodiment of the powdercloud device of FIG. 2. The development electrode is grounded orelectrically biased in the manner described in the above description ofthe development electrode 30 in FIG. 2. The surface of the developmentelectrode 40 in FIG. 3, however, includes a series of hemisphericprotrusions 41 which extend into the toner cloud flow as it passes thecharged image to effect turbulence in the flow. Such an inducedcondition of turbulence thereupon will cause the toner to pass thesurface to be developed in multiple directions to overcome the streakingeffects normally caused by undirectional development. The electrode 40may further be oscillated or orbited in a direction to and from the drumto produce still more turbulence in the flow for a greater reduction ofdirectional effects in development. Thus, the development electrodehaving hemispherical protrusions may remain stationary, be oscillated,or be orbited according to the degree of turbulence needed forsatisfactory development.

Oscillation of the development electrode may be accomplished by anysuitable motor means 42 or oscillation system. As an example, there isillustrated in FIG. 3 a small motor 42 mounted in suitable brackets 43beneath the surface of the electrode 40. A connecting rod 44 havingholes at both ends is pivotally connected at one end to a bracket 46including a stud which is affixed to the electrode and and at the otherend is pivotally connected to a stud 48 mounted on a disc member whichis rotated by the motor. The electrode is slidably mounted in brackets49 which allows it to move to and from the drum according to thecombined rotation of the disc and movement of the connecting rod.

Referring now to FIG. 4, there is illustrated still another embodimentof the development electrode 30 shown in FIG. 2, wherein the electrode50 of FIG. 4 includes tufts 51 of fibers of any suitable materialaffixed to its surface which extend toward the photoconductive drum. Thetufts 51, thereby, cause turbulence in the toner flow to eliminate thepreviously mentioned directional effects of development. This form ofthe electrode may also be oscillated to and from the charged image toinduce greater turbulence in the flow in the manner described foroscillation of the electrode shown in FIG. 3 or may be orbited in anymanner (not shown).

Referring now in particular to FIG. 5, there is illustrated a stillfurther embodiment of the development electrode utilized in the powdercloud device of FIG. 2. The electrode 60 of FIG. 5 includes a surfacehaving alternately oriented, perforated, funnel shape members 61 whichare oscillated to and fro in relation to the charged image in the mannerdescribed herein in conjunction with the embodiment of FIG. 3.Oscillation of the electrode similarly causes turbulence in the tonerflow to alleviate directional development effects as previouslydiscussed. As the funnels are oscillated, an airflow circulation iscreated through the funnels which acts to increase the turbulence of theflow.

Referring to FIG. 5, there is shown a schematic view of the electrode 60which illustrates the airflow circulation through the funnels whichcauses a turbulence in the toner cloud flow allowing the toner to passthe image in more than one direction. The electrode 60 of FIG. 5 issuitably grounded or biased in the manner described in the otherembodiments of the development electrode herein disclosed.

Referring now in particular to FIG. 6, there is illustrated anembodiment of a simplified version of the powder cloud developmentdevice 20 utilized at development station 5 according to the presentinvention. A housing 71 is suitably mounted adjacent to thephotoconductive surface to be developed and includes therein aconventional transverse blower 72. The transverse blower is aconventional transverse flow fan which creates a significantly higherpressure coefficient than other well-known fans resulting in a highervelocity flow than possible with other types of fans. The transverse fanis suitably mounted in the housing to create a clockwise flow of airaround the exterior of the fan as shown by the arrows. The upper portionof the housing includes an opening 73 which is adjacent to the latentimage bearing photoconductive surface. As a prevention for the loss oftoner to the outside of the device, seals 74 and 75 having low-frictioncharacteristics are mounted between the housing and the photoconductoron both sides thereof. Mounted on the housing adjacent and inconfronting relationship to the charged image is a development electrode76 which is a grounded conductive member or alternatively can beelectrically biased in the manner previously discussed in the embodimentof FIG. 2. The clockwise flow created by the transverse blower flowsfrom left to right through the space 77 between the developmentelectrode and the charged image and returns to the transverse fan forrecirculation. A suitable toner dispenser 78 is mounted near the bottomof the housing and includes a dispensing roller 79 of the typepreviously described in conjunction with the powder 5 cloud device ofFIG. 2. As toner is dispensed into the flow of air created by thetransverse fan, a toner cloud is formed which circulates around thehousing and through the space between the photoconductor drum 1 and thedevelopment electrode 76 to develop the image on the surface of the pho-1 toreceptor.

It has been found that the creation of high-velocity toner flow by useof a transverse blower as described herein alleviates the need for aprecipitation roller since the flow is 1 moving with such rapid speedthat the level of concentration in the flow is not a problem. Further,as a means to place a proper charge on the toner so as to allow it todevelop the charged image, the blades of the fan in this embodiment arecoated with a suitable material which forms a triboelectric relationshipto the toner whereby toner is given a suitable electrostatic charge asit flows through the fan in contact with the blades. The powder clouddevice as described in the embodiment of FIG. 7 further can utilize theturbulence inducing electrodes disclosed previously for use in theembodiment of 2 FIG. 2 in order to eliminate any directional orstreaking effects caused by the high-velocity flow herein described. Theuse of such a turbulence-inducing electrode along with the high-velocityconditions created by the transverse fan produces adequate developmentof the image without the 3 need of a concentration controller andprecipitation roller described in the embodiment of FIG. 2.

The novel powder cloud development devices disclosed in conjunction withthe present invention will effectively develop a charged image on anyphotoconductor, as for example, a 3 photoconductor surface on a belt, aweb, paper or the like. Further, it is within the scope of the inventionto vibrate the development electrode shown in the embodiments of FIG. 2and FIG. 7 without the use of the particular electrode surfacesdescribed in the embodiments of FIGS. 3 to 5 for the purpose of inducingturbulence in the toner flow.

While the invention has been described with reference to preferredembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents 4 may be substituted forelements thereof without departing from the true spirit and scope of theinvention. ln addition, many modifications may be made to adapt aparticular situation or material to the teaching of the inventionwithout departing from its essential teachings.

What is claimed is:

1. An apparatus for developing a support surface bearing a latentelectrostatic image with developer material comprising;

a supply of developer material,

fan means for generating a flow of air for carrying developer materialto the support surface bearing the l t ntde apz t image conducting meansconnecting Wfimmnrfieamerwnducting said flow of air past said supportsurface,

rotatable dispensing means having one portion of the surface thereofcommunicating with the developer material in said supply and havinganother portion of the surface thereof communicating with the airflow insaid conducting means for rotatably conveying said developer material onthe surface of said rotatable dispensing means from 6 said supply tosaid conducting means for introducing the developer on the surface ofsaid rotatable dispenser to said airflow. and

air return means for directing the airflow back to said fan means afterpassing the surface to be developed.

2. An apparatus for developing a support surface bearing a latentelectrostatic image as in claim l and further including,

a precipitator for removing unused developer material from the air ofthe flow of air after the airflow passes the surface to be developed.

3. The apparatus of claim 1 wherein the rotatable dispensing means is aroller made of a surface having a triboelectric relationship with thedeveloper material to place an electrostatic charge on the developermaterial.

4. The apparatus of claim 1 further including an electrically groundedconductive electrode spacedly mounted adjacent the image-bearing surfaceto cause developer material to flow therebetween.

5. The apparatus of claim 4 wherein the electrode further includesturbulence inducing means for effecting turbulence of the flow ofdeveloper material to eliminate directional development effects.

6. The apparatus of claim 5 wherein the turbulence-inducing means is aseries of protrusions on the surface of the electrode to extend into theflow of developer material.

7. An apparatus for developing a support surface bearing a latentelectrostatic image with developer material comprising;

fan means for creating a flow of air,

dispensing means mounted adjacent said flow of air for introducingelectrostatically charged developer material into the flow to be carriedthereby,

conveying means connected to the fan means and the dispensing means fordirecting the flow of air carrying charged developer material past asurface bearing a latent image to be developed, and

receiving means for directing the airflow back to the fan means afterpassing the surface to be developed, said receiving means including aprecipitator for removing unused developer material from the flow afterpassing the surface to be developed, said precipitator comprising aroller made of a material that forms a triboelectric relationship withthe developer material to allow developer to be collected thereon.

8. The apparatus of claim 7 further including a developer reservoirmounted adjacent the roller to receive developer material collectedthereon whereby the reservoir supplies developer to the dispensingmeans.

9. The apparatus of claim 7 wherein the roller includes scraper elementadapted to scrape off developer material collected thereon to allow itto be received by the reservoir.

10. An apparatus for developing a support surface bearing a latentelectrostatic image with developer material comprising;

fan means for creating a flow of air,

dispensing means mounted adjacent said flow of air for introducingelectrostatically charged developer material into the flow to be carriedthereby,

conveying means connected to the fan means and the dispensing means fordirecting the flow of air carrying charged developer material past asurface bearing a latent image to be developed, and

receiving means for directing the airflow back to the fan means afterpassing the surface to be developed, said receiving mean s includin g aprecipitator fo rremoving unused developer material from the flow afterpassing the surface to be developed, said precipitator including aroller coupled to a bias potential of opposite polarity than the chargeon the developer to attract developer thereto.

11. An apparatus for developing a support surface bearing a latentelectrostatic image with developer material comprising;

fan means for creating a flow of air,

dispensing means mounted adjacent said flow of air for in troducingelectrostatically charged developer material into the flow to be carriedthereby,

conveying means connected to the fan means and the dispensing means fordirecting the flow of air carrying charged developing material past asurface bearing a latent image to be developed, and

receiving means for directing the airflow back to the fan means afterpassing the surface to be developed, said receiving means including aprecipitator for removing unused developer material from the flow afterpassing the surface to be developed and a baffle member coupled to anelectrical bias potential as the same polarity as the charge on thedeveloper material to repel developer material therefrom to theprecipitator.

12. An apparatus for developing a support surface bearing a latentelectrostatic image with developer material comprising;

fan means for creating a flow of air,

dispensing means mounted adjacent said flow of air for introducingelectrostatically charged developer material with the flow to be carriedthereby,

conveying means connected to the fan means and the dispensing means fordirecting the flow of air carrying charged developing material past asurface bearing a latent image to be developed,

an electrically grounded conductive electrode spacedly mounted adjacentthe image-bearing surface to cause developer material to flowtherebetween, said electrode including turbulence inducing means foreffecting turbulence of the flow of developer material to eliminatedirectional development effects and said turbulence inducing meansincludes a series of tufts of fibers mounted on the surface of theelectrode to extend with the flow of developer material, and

receiving means for directing the airflow back to the fan means afterpassing the surface to be developed.

13. An apparatus for developing a support surface bearing a latentelectrostatic image with developer material comprising;

fan means for creating a flow of air,

dispensing means mounted adjacent said flow of air for introducingelectrostatically charged developer material into the flow to be carriedthereby,

conveying means connected to the fan means and the dispensing means fordirecting the flow of air carrying charged developing material past asurface bearing a latent image to be developed.

an electrically grounded conductive electrode spacedly mounted adjacentthe image-bearing surface to cause the developer material to flowtherebetween, said electrode including turbulence inducing means foreffecting turbulence of the flow of developer material to eliminatedirectional development effects, said turbulence inducing meansincluding vibrating means connected to the electrode to move theelectrode to and from the image bear ing surface, and

receiving means for directing the airflow back to the fan means afterpassing the surface to be developed.

14. The apparatus of claim 12 wherein the electrode includes a surfaceof alternatively directed perforated funnels to create an additionalairflow through the perforations to effect turbulence of the flow ofdeveloper material.

15. In an apparatus for developing a support surface bearing a latentelectrostatic image with developer material including a developer flowgenerator for moving charged developer in a fluid flow medium past animage bearing surface to be developed, the improvement thereincomprising a turbulence inducing means mounted adjacent the developermaterial flow passing the image-bearing surface to be developed toprevent directional development effects, said turbulence-inducing meansincluding an electrically grounded development electrode, saiddevelopment electrode being vibrated relative to the image-bearingsurface to be developed to induce turbulence.

16. The device of claim 15 wherein the electrode includes a series ofelements extending into the developer material flow to create turbulencetherein.

17. In an apparatus for developing a support surface bearing a latentelectrostatic image with developer material including a developer flowgenerator for moving charged developer in a fluid flow medium past animage bearing surface to be developed, the improvement thereincomprising a turbulence inducing means mounted adjacent the developermaterial flow passing the surface bearing the latent electrostatic imageto be developed to prevent directional development effects, saidturbulence inducing means including;

an electrically grounded development electrode for repelling chargeddeveloper in the developer material flow, and means for oscillating saiddevelopment electrode relative to said image bearing surface forinducing turbulence in the developer material flow as said developermaterial flow passes the surface bearing the latent electrostatic image.

1. An apparatus for developing a support surface bearing a latentelectrostatic image with developer material comprising; a supply ofdeveloper material, fan means for generating a flow of air for carryingdeveloper material to the support surface bearing the latentelectrostatic image, conducting means connecting with said fan means forconducting said flow of air past said support surface, rotatabledispensing means having one portion of the surface thereof communicatingwith the developer material in said supply and having another portion ofthe surface thereof communicating with the airflow in said conductingmeans for rotatably conveying said developer material on the surface ofsaid rotatable dispensing means from said supply to said conductingmeans for introducing the developer on the surface of said rotatabledispenser to said airflow, and air return means for directing theairflow back to said fan means after passing the surface to bedeveloped.
 2. An apparatus for developing a support surface bearing alatent electrostatic image as in claim 1 and further including, aprecipitator for removing unused developer material from the air of theflow of air after the airflow passes the surface to be developed.
 3. Theapparatus of claim 1 wherein the rotatable dispensing means is a rollermade of a surface having a triboelectric relationship with the developermaterial to place an electrostatic charge on the developer material. 4.The apparatus of claim 1 further including an electrically groundedconductive electrode spacedly mounted adjacent the image-bearing surfaceto cause developer material to flow therebetween.
 5. The apparatus ofclaim 4 wherein the electrode further includes turbulence inducing meansfor effecting turbulence of the flow of developer material to eliminatedirectional development effects.
 6. The apparatus of claim 5 wherein theturbulence-inducing means is a series of protrusions on the surface ofthe electrode to extend into the flow of developer material.
 7. Anapparatus for developing a support surface bearing a latentelectrostatic image with developer material comprising; fan means forcreating a flow of air, dispensing means mounted adjacent said flow ofair for introducing electrostatically charged developer material intothe flow to be carried thereby, conveying means connected to the fanmeans and the dispensing means for directing the flow of air carryingcharged developer material past a surface bearing a latent image to bedeveloped, and receiving means for directing the airflow back to the fanmeans after passing the surface to be developed, said receiving meansincluding a precipitator for removing unused developer material from theflow after passing the surface to be developed, said precipitatorcomprising a roller made of a material that forms a triboelectricrelationship with the developer material to allow developer to becollected thereon.
 8. The apparatus of claim 7 further including adeveloper reservoir mounted adjacent the roller to receive developermaterial collecTed thereon whereby the reservoir supplies developer tothe dispensing means.
 9. The apparatus of claim 7 wherein the rollerincludes scraper element adapted to scrape off developer materialcollected thereon to allow it to be received by the reservoir.
 10. Anapparatus for developing a support surface bearing a latentelectrostatic image with developer material comprising; fan means forcreating a flow of air, dispensing means mounted adjacent said flow ofair for introducing electrostatically charged developer material intothe flow to be carried thereby, conveying means connected to the fanmeans and the dispensing means for directing the flow of air carryingcharged developer material past a surface bearing a latent image to bedeveloped, and receiving means for directing the airflow back to the fanmeans after passing the surface to be developed, said receiving meansincluding a precipitator for removing unused developer material from theflow after passing the surface to be developed, said precipitatorincluding a roller coupled to a bias potential of opposite polarity thanthe charge on the developer to attract developer thereto.
 11. Anapparatus for developing a support surface bearing a latentelectrostatic image with developer material comprising; fan means forcreating a flow of air, dispensing means mounted adjacent said flow ofair for introducing electrostatically charged developer material intothe flow to be carried thereby, conveying means connected to the fanmeans and the dispensing means for directing the flow of air carryingcharged developing material past a surface bearing a latent image to bedeveloped, and receiving means for directing the airflow back to the fanmeans after passing the surface to be developed, said receiving meansincluding a precipitator for removing unused developer material from theflow after passing the surface to be developed and a baffle membercoupled to an electrical bias potential as the same polarity as thecharge on the developer material to repel developer material therefromto the precipitator.
 12. An apparatus for developing a support surfacebearing a latent electrostatic image with developer material comprising;fan means for creating a flow of air, dispensing means mounted adjacentsaid flow of air for introducing electrostatically charged developermaterial with the flow to be carried thereby, conveying means connectedto the fan means and the dispensing means for directing the flow of aircarrying charged developing material past a surface bearing a latentimage to be developed, an electrically grounded conductive electrodespacedly mounted adjacent the image-bearing surface to cause developermaterial to flow therebetween, said electrode including turbulenceinducing means for effecting turbulence of the flow of developermaterial to eliminate directional development effects and saidturbulence inducing means includes a series of tufts of fibers mountedon the surface of the electrode to extend with the flow of developermaterial, and receiving means for directing the airflow back to the fanmeans after passing the surface to be developed.
 13. An apparatus fordeveloping a support surface bearing a latent electrostatic image withdeveloper material comprising; fan means for creating a flow of air,dispensing means mounted adjacent said flow of air for introducingelectrostatically charged developer material into the flow to be carriedthereby, conveying means connected to the fan means and the dispensingmeans for directing the flow of air carrying charged developing materialpast a surface bearing a latent image to be developed. an electricallygrounded conductive electrode spacedly mounted adjacent theimage-bearing surface to cause the developer material to flowtherebetween, said electrode including turbulence inducing means foreffecting turbulence of the flow of developer material to eliminatedirectional developmeNt effects, said turbulence inducing meansincluding vibrating means connected to the electrode to move theelectrode to and from the image bearing surface, and receiving means fordirecting the airflow back to the fan means after passing the surface tobe developed.
 14. The apparatus of claim 12 wherein the electrodeincludes a surface of alternatively directed perforated funnels tocreate an additional airflow through the perforations to effectturbulence of the flow of developer material.
 15. In an apparatus fordeveloping a support surface bearing a latent electrostatic image withdeveloper material including a developer flow generator for movingcharged developer in a fluid flow medium past an image bearing surfaceto be developed, the improvement therein comprising a turbulenceinducing means mounted adjacent the developer material flow passing theimage-bearing surface to be developed to prevent directional developmenteffects, said turbulence-inducing means including an electricallygrounded development electrode, said development electrode beingvibrated relative to the image-bearing surface to be developed to induceturbulence.
 16. The device of claim 15 wherein the electrode includes aseries of elements extending into the developer material flow to createturbulence therein.
 17. In an apparatus for developing a support surfacebearing a latent electrostatic image with developer material including adeveloper flow generator for moving charged developer in a fluid flowmedium past an image bearing surface to be developed, the improvementtherein comprising a turbulence inducing means mounted adjacent thedeveloper material flow passing the surface bearing the latentelectrostatic image to be developed to prevent directional developmenteffects, said turbulence inducing means including; an electricallygrounded development electrode for repelling charged developer in thedeveloper material flow, and means for oscillating said developmentelectrode relative to said image bearing surface for inducing turbulencein the developer material flow as said developer material flow passesthe surface bearing the latent electrostatic image.